1. Field of the Invention
The present invention relates to a composition active as an algaecide and a herbicide. In particular, the present invention relates to a composition for use in aquatic environments to control weeds and algae.
2. Brief Description of Related Art
Aquatic environments, such as rivers, canals and ponds, are frequently subject to excessive plant growth which blocks the flow of water and leads to stagnation. As fertilizers and growth promoters wash in to the water from agricultural land, the problem becomes more severe as plant growth increases.
Other aqueous environments, such as swimming pools, shower rooms and storage tanks are often polluted by algal growth which affects the color of the water and can be harmful to water users. Growth in fishponds can be particularly harmful due to the toxic nature of some algae.
The prior art shows that plant and algae growth can be restricted by the use of copper ions. However, such treatment methods are often unsuited for use in flowing water systems.
Copper sulfate has been used for algae control. It is granular and generally applied as such, although it can be dissolved in water and applied as a solution. However, there are problems associated with the use of copper sulfate since the chemical is not stable in water. When applied, copper ions react with carbonates present in the water to produce the insoluble copper carbonate salt which precipitates out of solution. In this form, the copper is no longer bioavailable and so will not control weeds or algae. To overcome this, large doses of copper sulfate are used to compensate for the conversion to copper carbonate. However, over an extended period of time, it is envisaged that accumulated deposits of precipitated carbonate which settle in the mud on the bottom of streams, ponds, irrigation systems and the like may have detrimental effects on the environment. Furthermore, copper sulfate, when used at its maximum legally permissible usage level, will not destroy pondweed.
The use of copper in complexed form has also been proposed. U.S. Pat. No. 2,734,028 discloses a complex formed between copper sulfate and alkanolamines. The copper ions remain in solution even in the presence of carbonates. However, the complex breaks down during storage and when diluted loses its effectiveness.
U.S. Pat. No. 3,930,834 discloses chelated copper ions. Copper compounds are reacted with acid to dissociate copper ions. These are then chelated with, e.g. alkanolamine, tertiary amine and carboxylic acid. The copper remains soluble over a longer period of time than when applied as simple copper sulfate and is more bioavailable to the algae and plants.
However, chelated copper is still not satisfactory in flowing irrigation systems since, even when used at its maximum legally permissible usage level, it tends to be rapidly diluted out before it is able to kill the target algae. Furthermore, the maximum legally permissible usage level is not sufficient to kill pondweed.
Other non-copper based systems are known. For example 2-propenal is used to control weeds and algae in flowing irrigation systems. However, it is highly flammable and toxic. Severe restrictions have been placed upon its use. Herbicides such as Aquathol.TM. and diquat control aquatic weeds but there are restrictions on the use of such treated water for irrigation.
There is therefore a need for a system which is effective as an algaecide and herbicide in flowing water systems, which satisfies environmental controls and which is safe for fish and use in irrigation supplies.